Okay, let's begin. It seems logical to say the Empire of the OT was formed on clones, it was the fastest way to grow an enormous army that would be used for Galaxy-wide domination. Now, that's not to say that every trooper (whether it by TIE Fighter pilot, stormtrooper, etc) is a clone. I believe that by the time of ANH there are many clones still running around, but the numbers of people who desire to be stormtroopers has increased (think about the propoganda; people probably viewed stromtroopers like Roman soldiers, they wanted to be one because it was cool). We also know that by ANH, cloning had been illegalized; now, that does not mean it didn't happen, but then why all the shock in the final scenes of Dark Force Rising when Luke and the others found out about the clone stromtroopers aboard the Katana? Simple, clones had become a thing of the past. I mean, the EU is riddled with allusions to mad clones and, undoubtedly, people in the galaxy had started to view clones as a bad thing. Palpatine, being the political genius he is, would probably have exploited that image of ma/bad clones to help recruitment efforts of regular peoples. I mean, after all, it's easier to control people if their own kind are the ones doing the controlling versus having outside forces coming in and doing it (i.e. clones). We also know that recuritment efforts for non-clones had long since been happening in SW. For instance, we had Kyp Durron's brother in Champions of the Force who was not a clone. You can't go into the military and expect to become a clone, but you certainly want to be like one (if the idea that clones are looked at badly is accepted). I agree with Imperator2 on the idea of covering people's faces with helmets for "scary" reasons. But I have to go with Jahled on the idea that those with helmets are, or at least at one point were all clones. I believe that just about every unit in SW that has a "faceless helmet" on was probably clone at one time or another, but the evidence lies in the movies and EU that all stormtroopers (and others) are not clones. In ANH itself we have one voice yell "Close the blast doors!" and then a totally different (and deeper) voice yell "Open the blast doors! Open the blast doors!" Then we have the stormtrooper who nearly apprehended Leia and Han in ROTJ say "Freeze!" in a voice unlike those two of ANH. Then he have the scout troopers who try to apprehend Leia in the forest with Wickit...the list goes on and on. Conclusion, the Empire's military was founded on clones. Millions, maybe even billions of clones, but the practice of cloning, for some reasons, disappeared by at least the time of ANH (that's not to say that Clone troopers weren't still in the military; they would be "late models"). Then we have Grand Admiral Thrawn walk onto the scene and discover the cloning facilities in Mount Tantiss on Wayland. Now, this raises the quesiton of whether these facilities were used by the Empire in secret during the OT. Possibly and if so, probably for elite units like the Imperial Royal Guard and the 501st "Emperor's Fist". Regardless, clones had very obviously fallen out of use by the Empire until Thrawn restarted the facilities there (thus we get the surprised reactions of our heroes aboard the Katana in Dark Force Rising). Mount Tantiss is then destroyed, but we know that Thrawn took at least one cloning cylinder to the Nirana and spread clone "sleeper cells" throughout the galaxy. Thus we get some of the action and characters (specifically the Soontir Fel clones) in Specter of the Past and Vision of the Future. We know, though, that between The Last Command and Specter of the Past, cloning was in total disuse (we have the evidence of the training facilities where Kyp Durron's brother was in Champions of the Force, and we have a comment in Darksaber about how those dressed as Royal Guards are not real guardsmen but "merely" stormtroopers wearing the armor, giving us a hint at the Empire's lack of resources, specifically its man power). Beyond that...well, I don't believe clones were mentioned very much if at all in the NJO, but I could be mistaken. By the way, the 501st mentioned in Zahn's Survivor's Quest was probably a unit that called itself for the conotation the 501st had, but was very likely not the original. So I agree with Jahled that the Empire was founded on clones, but then I believe the Empire started recruiting, mixing clone troops with "real" troops.
